What is the importance of lac operon?

The classic example of prokaryotic gene regulation is that of the lac operon. This operon is a genetic unit that produces the enzymes necessary for the digestion of lactose (Fig. 16-13). The lac operon consists of three contiguous structural genes that are transcribed as continuous mRNA by RNA polymerase.

How does the lac operon regulate the production of the enzymes needed to metabolize lactose?

Sample answer: The lac operon regulates the production of the enzymes needed to metabolize lactose in the following ways: • In the absence of lactose, the upstream lacI gene synthesizes the lac repressor protein, which binds to the lac operator to stop RNA polymerase from binding and stop the transcription of the lacZ.

Can lactose induce lac operon?

Allolactose is an isomer of lactose and is the inducer of the lac operon. Lactose is galactose-β(1→4)-glucose, whereas allolactose is galactose-β(1→6)-glucose. Lactose is converted to allolactose by β-galactosidase in an alternative reaction to the hydrolytic one.

What is the function of lactose in the lac operon quizlet?

In the case of the lac operon, lactose is the inducer. If lactose is present, it binds to and inactivates the repressor by causing it to fall off the operator. If lactose operator is free of repressor, then RNA Polymerase is able to bind.

How does the lac operon regulate lactose digestion in bacteria?

The lac, or lactose, operon is found in E. coli and some other enteric bacteria. This operon contains genes coding for proteins in charge of transporting lactose into the cytosol and digesting it into glucose. This glucose is then used to make energy.

How does lactose turn on the lac operon?

When lactose is available, some molecules will be converted to allolactose inside the cell. Allolactose binds to the lac repressor and makes it change shape so it can no longer bind DNA. Allolactose is an example of an inducer, a small molecule that triggers expression of a gene or operon.

What happens to the lac operon in the absence of lactose?

When lactose is absent the lac operon is switched off. This is becasue a repressor protein is produced which binds to the operator region. This prevetns RNA polymerase from binding to the operon and therefore prevents transcription of the structual genes.

How does the lac operon know to be turned on when lactose is present?

Normally, the lac operon is turned off. A repressor protein binds the operator (control) region upstream of the operon preventing transcription. When lactose is present outside the cell, it crosses the cell membrane and acts as an inducer of the operon. It does so once lactose is broken down to create allolactose.

What is the role of lactose as an inducer in lac operon?

Explain the role of lactose as an inducer in a lac operon. Lactose acts as an inducer in Lac operon by binding to the repressor protein, the repressor protein is produced by the inhibitory gene ( LacI) present upstream to the operon gene.

What is the function of the lac operon in E coli?

The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when lactose is present and glucose is absent. Two regulators turn the operon “on” and “off” in response to lactose and glucose levels: the lac repressor and catabolite activator protein (CAP).

What genes are involved in lactose utilization?

Regulation of genes for lactose utilization. lac repressor, catabolite activator protein, and cAMP. The lac operon of E. coli contains genes involved in lactose metabolism. It’s expressed only when lactose is present and glucose is absent.

How does the lac repressor act as a lactose sensor?

The lac repressor acts as a lactose sensor. It normally blocks transcription of the operon, but stops acting as a repressor when lactose is present. The lac repressor senses lactose indirectly, through its isomer allolactose. Catabolite activator protein ( CAP) acts as a glucose sensor.